through the Quest 3

Yes. In the UI, the headset uses a lower resolution than it is capable of, and there is no setting available in the Settings menus to adjust this (unless you use SideQuest or Quest Game Optimizer). I've also noticed that when looking at menus, especially in focus mode, the background virtual environment goes into low-quality mode, probably to increase performance and extend the battery charge. In games, the developer can force higher graphics settings, so the games tend to look better.